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Ch. 6: Diamond

Ch. 6: Diamond Page of 515 Ch. 6: Diamond Text size:minus plus Restore normal size   Mail page  Print this page
194                     A POPULAR TREATISE ON GEMS.
real ones, and faulty ones instead of pure diamonds. The officers of the Junta Diamontina test the rough stones by holding them whilst rubbing together, close to the ear, and listening to the tone produced, which gives them ample satisfaction of their being genuine, as it is only to be ob­served in real diamonds. It requires, however, consider­able practice to distinguish them with accuracy by this test. Strangers particularly, are imposed upon by the negroes in Brazil, by purchasing from them gems cut and polished with the facets, resembling those of the diamond; and although any one acquainted with the diamond will soon detect the imposition by the want of specific weight, the peculiar lustre, fire, and hardness, he requires to be on his guard. If, however, the diamond is ascertained to be genuine, we have to examine particularly its purity, color, form, and size, these being the qualities by which the price of a rough diamond is to be determined.
It requires considerable experience to determine from a rough diamond whether any of its faults are at the surface or in the interior, whereby often the diamond, in removing all its faults, may be diminished to half its size. We often, however, judge the rough stones by their color; those turning towards the green color are considered to be the best; those of a reddish color to be good stones; the black color indicates a hard stone; and we judge a yellowish or grayish color as making bad diamonds. The natural form of a diamond, likewise, gives a characteristic to the pur­chaser of rough stones ; for a flat, thin, or triangular stone would lose much in the grinding, and not be so high as to give it sufficient fire ; and likewise we are not sure of the result of the cutting, and the hemitrope crystals are very difficult to work. The best forms of diamonds for cutting are the octahedron, which is principally found in the East Indies, and is called Pint by the diamond-grinders; and the
Ch. 6: Diamond Page of 515 Ch. 6: Diamond
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